---
title: "Instrument Caches"
description: "Learn how to manually instrument your code to use Sentry's Caches module. "
url: https://docs.sentry.io/platforms/go/guides/fiber/tracing/instrumentation/caches-module/
---

# Instrument Caches | Sentry for Fiber

Sentry offers a cache-monitoring dashboard that can be auto-instrumented by some SDKs. If you're Go, you can manually instrument your cache operations and use Sentry to monitor your caching performance to get a look into how your caching solution is performing by following the setup instructions below.

To allow Sentry to track cache performance, you'll need to create two spans:

* One for when an item is put into the cache.
* Another for when an item is fetched from the cache.

Ensure there is an active transaction when creating the spans. For more information, see [Tracing](https://docs.sentry.io/platforms/go/guides/fiber/tracing.md).

For detailed information about the available data, see the Cache Module developer specification.

## [Custom Instrumentation](https://docs.sentry.io/platforms/go/guides/fiber/tracing/instrumentation/caches-module.md#custom-instrumentation)

As the GO SDK does not support auto cache instrumentation, you'll need to manually instrument the Cache Module as described below.

### [Add Span When Putting Data Into the Cache](https://docs.sentry.io/platforms/go/guides/fiber/tracing/instrumentation/caches-module.md#add-span-when-putting-data-into-the-cache)

Use custom instrumentation to emit spans for cache data.

* Set the cache value using your preferred cache library.
* Wrap the part of your application that adds data to the cache in a span.
* Set `op` to `cache.put`.
* Optionally, set `cache.item_size` to the size of the cached item.

#### [Example (Go)](https://docs.sentry.io/platforms/go/guides/fiber/tracing/instrumentation/caches-module.md#example-go)

```go
key := "cache_key"
value := "cache_value"

parentSpan := sentry.StartSpan(context.Background(), "parent_span")

if parentSpan != nil {
    span := parentSpan.StartChild("cache.put")
    defer span.Finish()

    // Perform the cache operation
    err := cache.Put(key, value)

    span.SetData("network.peer.address", "127.0.0.1")
    span.SetData("network.peer.port", 9000)
    span.SetData("cache.key", key)
    span.SetData("cache.item_size", len(value))

    if err != nil {
        span.SetTag("error", err.Error())
    }
}
```

### [Add Span When Retrieving Data From the Cache](https://docs.sentry.io/platforms/go/guides/fiber/tracing/instrumentation/caches-module.md#add-span-when-retrieving-data-from-the-cache)

For unsupported cache solutions, use custom instrumentation to emit cache spans:

Fetch the cached value using your preferred cache library. Wrap the part of your application that retrieves data from the cache in a span. Set op to cache.get. Set cache.hit to true or false, depending on whether the value was found. Optionally, set cache.item\_size to the size of the retrieved item.

Example:

```go
key := "cache_key"
var value string

parentSpan := sentry.StartSpan(context.Background(), "parent_span")

if parentSpan != nil {
    span := parentSpan.StartChild("cache.get")
    defer span.Finish()

    // Perform the cache operation
    value, err := cache.Get(key)

    span.SetData("network.peer.address", "127.0.0.1")
    span.SetData("network.peer.port", 9000)
    span.SetData("cache.key", key)

    if err == nil && value != "" {
        span.SetData("cache.hit", true)
        span.SetData("cache.item_size", len(value))
    } else {
        span.SetData("cache.hit", false)
    }
}
```

You should now have the right spans in place. Head over to the [Cache dashboard](https://sentry.io/orgredirect/organizations/:orgslug/insights/backend/caches/) to see how your cache is performing.